If he succeeds, he’ll be the first person ever to complete the 9,000km swim.

It would be a massive achievement – and experienced long-distance open water swimmers are already in awe of his attempt.

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Media captionBen Lecomte sets off as he attempts to become the first person to swim the Pacific Ocean

“It’s a mammoth task and I have full respect for him but he is going to be going through quite a lot of pain at some points during those six months,” 23-year-old PhD student André Roberts tells Radio 1 Newsbeat.

André swam the channel in 2015, a 13-hour stroll-in-the-park compared to what Ben is attempting.

Ben, who’s 51, is hoping to cross the Pacific to raise awareness of global warming while a team of scientists on a support boat conduct research on both him and the stretch of water.

But Ben will face a string of obstacles – physical, mental and fish-based – which will make his ocean crossing extremely difficult.

The chafing (and muscles) will need constant attention

Image copyrightAndré Roberts

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André swam the British Channel in 2015

“He’s in a wetsuit so for starters you have the chafing,” says André.

“There’s going to be a lot of Vaseline needed because otherwise that’s going to be really painful. He will be rubbing raw.”

André says that after he swam the channel, he suffered extreme cramps for several days – meaning Ben’s team will have to take special measures to take care of his physical health.

“His muscles are going to need continuous sports injury treatment because they’re going to be so sore,” he says.

Then there’s the worry of what he’ll bump into along the way.

There will be sea life that stings – or worse

Image copyrightKeri-anne Payne

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Keri-anne Payne says jellyfish are her “least favourite aquatic animals” and that their stings feel like stinging nettles

“There were about 2,000 jellyfish just hanging around, which was slightly concerning before we started the swim.”

Keri-anne says she still has “a few little scars” from her jellyfish encounters in Australia and that every time she gets out in the open ocean by herself she thinks something is “on its way to get me”.